The proposed K08 career development award application describes a 5-year program for the support of the principal investigator, Dr. Kim-Hien Dao, who is a clinician scientist in the transitional phases of developing an independent research program at Oregon Health & Science University (OHSU). Dr. Dao's research experience began with her PhD training in the area of cancer biology and RAS signaling in human fibro sarcoma cell lines. After Internal Medicine residency training, she completed fellowship training in Hematology-Oncology at the University of California at San Diego. Through this experience, as a Clinical Fellow Scholar in the California Institute for Regenerative Medicine Program, she acquired a 2-year postdoctoral research experience under the direction of Dr. Catriona Jamieson and was introduced to hematopoietic stem cell biology. The current application outlines additional years of mentored research with a formal career development plan under the guidance of Drs. Grover Bagby and Brian Druker. Dr. Dao will take advantage of an advisory committee composed of highly successful, NIH-funded medical scientists at OHSU and a research environment with internationally-recognized expertise in Fanconi Anemia (FA) research, stem cell biology, cancer cell biology, and tyrosine kinase signaling. The research proposed will focus on investigating why loss of function mutations in genes of the FA pathway, classically described as a DNA damage response pathway, give rise to hematopoietic stem cells with inherent defects in stem cell fitness. The overall hypothesis is that the FA core complex is involved in stabilizing the nuclear function of beta-catenin and the disruption of this interaction is the molecular basis for the limited replicative and survival potential of FA deficiet hematopoietic stem cells. The main objective is to mechanistically define the interaction between FA pathway and Wnt/beta-catenin signaling. The specific aims include: 1) Determine whether proteins of the FA core complex increase protein stability and/or nuclear localization of beta-catenin; 2) Determine whether FANCL directly mono-ubiquitinates beta-catenin leading to its enhanced nuclear activity; and 3) Define specific perturbations in Wnt/beta-catenin signaling in FA-deficient hematopoietic stem cells during development and bone marrow failure in an in vivo model of FA. If the susceptible pool of hematopoietic stem cells to malignant clonal evolution is defined by deficient Wnt/beta-catenin signaling, then disease progression in patients with bone marrow failure might be subverted by manipulating targets of the Wnt/beta-catenin pathway that would restore the fitness of the hematopoietic stem cells in a selective microenvironment. The mentored K08 award will directly advance her scientific development by protecting her effort towards her research project and career development plan. These transitional steps are necessary for her to achieve her long-term career goal of becoming a productive, independent researcher in academic medicine with sustained extramural funding.